The use of cylindrical drums which employ various heat transfer media to heat their outer surfaces, and the use of these drums in various processes requiring such heat to be applied to various materials, such as textile web materials, disposed on the drum surface, is well known. Generally, these cylindrical rotatable heat-transfer drums have employed various heat-transfer media, including steam and certain hydrocarbon liquids.
For example, it has been known to supply steam to the interior of such cylindrical heat-transfer drums in order to heat the outer surface thereof. Thus, in U.S. Pat. No. 2,932,091 such a rotatable drum, used for drying purposes, is disclosed. The apparatus there taught includes a central hollow thick-walled piper for the supply of steam to radially extending distributors, and then to a large plurality of parallelly spaced tubes lying about the inner periphery of the drum itself, and then to a second set of radial angularly spaced spokes or tubes at the opposite end of said drum for return of the steam. The use of such an apparatus, however, requires various condensate headers in order to prevent obstruction of the steam passage by condensate forming within the parallelly spaced tubes, and thus disturbing the heat transfer process. It is thus also necessary to impart the steam itself through these tubes at high velocities, in order to hold down condensation, and to additionally scavenge condensate which has formed therein. The use of steam has also raised other difficulties, including problems of rust and corrosion, as well as the necessity to employ massive heavy equipment.
In an attempt to solve these problems, the use of various fluid media, such as hydrocarbons, has been suggested. Thus, U.S. Pat. 3,228,462 teaches such a heat-exchange apparatus, or cylindrical drum, which utilizes such fluids as a heat-transfer media for heating the outer cylindrical surface thereof. The patentee thus teaches concentrically disposed inner and outer shells which are separated by parallel partitions, for the supply of such a medium to the surfaces of the cylindrical drum for allegedly uniform heating thereof. The patentee also provides independent, internested, labyrinthine flow channels which extend around the periphery of the drum, and thus cause the heat transfer medium to flow in opposite directions through these channels, each such flow channel beginning at one end of the drum, and ending at the other. Thus, while the patentee attempts to place adjacent each other hotter and cooler legs in order to attempt to equalize the surface temperature of the outer shell, the apparatus taught includes all feed means for hot heat-transfer fluid at one end of the drum, and all return means for cool heat-transfer fluid at the other. In addition, use of such multi-path labyrinthine channels, even in large numbers, requires a relatively long flow path for the medium within each such flow channel, thus permitting substantial cooling of this medium during its flow therethrough. This, in turn, requires the excessive heating of the heat transfer media prior to its entrance into any given flow channel.
It is an object of the present invention to provide an improved cylindrical heat-transfer drum, which overcomes these deficiencies of the prior art drums.
It is another object of the present invention to provide such a cylindrical heat-transfer drum which enables the efficient use of a heat-transfer medium for the substantially uniform heating of the outer cylindrical surface thereof.
It is yet another object of the present invention to provide such a cylindrical heat-transfer drum which does not require the excessive pre-heating of a heat-transfer medium used to obtain substantially uniform heating of the cylindrical surface thereof.
It is yet another object of the present invention to provide such a cylindrical heat-transfer drum which achieves substantially uniform heating of the surface thereof with a fluid heat-transfer medium, and which is relatively simple and inexpensive to produce.